ATR index, whose full name is Average true range, was developed by J. Welles Wilder and first mentioned in his book New Concept of Technical Analysis System (1978). This indicator is the trading fluctuation range after the average of N-day moving average price, and the general time period is 14 trading days. Of course, the specific value depends on your trading strategy. ATR is a commonly used indicator in foreign exchange trading and a classic indicator of stock futures. Basically, all market software comes with it.